Individual and joint Summit accounts are exactly the same in terms of account features (interest rate, ATM reimbursements, etc.). A joint account is only different in that it has two owners instead of one.
Both owners on a Joint account have equal access to all of the funds in the account, and equal ownership rights over these assets.
Both owners get their own debit card with a unique card number, and can manage the settings on their cards (e.g. travel notice) independently.
Like individual Summit accounts, joint account holders have the option to set a monthly Pay What Is Fair tip. The tip is deducted from the account once monthly.